6,321 research outputs found

    Ground-Based Observations of Recovery Phase Aurora

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    This analysis focuses on spatial and temporal forms occurring after substorm breakup. The observations show irregular shapes and nonuniform drifts with respect to relatively stationary pulsating patches. The pulsating patches occur within a diffuse auroral background as a modulation of the auroral brightness in a localized region. The images analyzed show a decrease in the brightness of the diffuse background in the region of the pulsating patch at the beginning of the 'off' phase of the modulation. Throughout the off phase the brightness of the diffuse aurora gradually increases back to the average intensity. The time constant for this increase is measured as the first step toward determining the physical process

    Formation of contacts between doped carbon nanotubes and aluminum electrodes

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    A theoretical study of the a semiconducting carbon nanotube (CNT) bonding to an aluminum electrode is presented using density functional theory to determine the electronic structure, and charge transport across the junction is studied using non-equilibrium Green's functions. The properties of CNT-metal junctions are of interest for optimizing metal-semiconductor junctions for Schottky barrier transistors and for the formation of Ohmic contacts for nanoelectronics. We first consider the properties of an undoped (16,0) CNT bonded to an aluminum electrode, including an analysis of metal induced gap states and examination of the surface dipole. The junction is then modified by introduction of substitutional dopants into the CNT using nitrogen and boron to form n- and p-type semiconductors, respectively, and the resulting impact of the doping on current transport across the junctions is calculated. As an alternative doping strategy, tetrathiafulvalene is introduced endohedrally and found to act as an n-type dopant in agreement with previous experimental studies. From electron transmission and current voltage characteristics, it is found that the doped junctions can be engineered to have much lower onset resistances relative to the undoped junction. It is found that the current-voltage characteristics display increased resistance for larger forward and reverse biases: For one polarity, the resistance increase is associated with the introduction of the CNT band gap into the voltage bias window, whereas for the opposing voltage polarity, the resistance increase is due to large charge carrier-substitutional dopant scattering. For the case of the endohedral doping scheme, it is found that the carrier-dopant scattering is effectively absent. (C) 2013 AIP Publishing LLC

    Medición de las condiciones habitacionales: una propuesta metodológica para analizar desigualdades inter e intraterritorios urbanos

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    La medición de las condiciones habitacionales de un territorio resulta de especial interés para la implementación de políticas públicas. Los métodos tradicionales se concentran en la medición de los déficits y dejan de lado aquella parte de la población que se encuentra cerca del umbral. Con base en propuestas específicas, estándares de organismos internacionales, legislación nacional y la importante participación de especialistas, en este estudio se genera una metodología cuantitativa, que evita esa pérdida de información al incluir a toda la población de un territorio, asignándole un puntaje a cada persona de acuerdo a las características del hogar que habita. Para validar la propuesta, se presenta una aplicación con datos de Argentina, donde se constata su versatilidad, dado que permite detectar problemáticas particulares en cada dimensión, y también consigue analizar el nivel promedio, la distribución intra e interterritorios y la pérdida de bienestar por desigualdad.The measurement of the housing conditions of a territory is particularly important for the implementation of public policies. Traditional methods focus on the measurement of deficits and leave aside that part of the population which is closer to the threshold. Based on specific proposals, the standards of international organizations, national legislation, and a significant participation of specialists, this study proposes a quantitative methodology, which avoids said loss of information by including the entire population of a territory, assigning a score to each person according to the characteristics of the household they live in. To validate this proposal, we present an application with data from Argentina, where its versatility is verified given that it allows for the detection of issues in each dimension while also getting to analyze the average level, the intra and interterritorial distribution, and the welfare loss due to inequality.Fil: Actis Di Pasquale, Eugenio. Universidad Nacional de Mar del Plata. Facultad de Ciencias Económicas y Sociales; Argentina

    RNA-seq reveals post-transcriptional regulation of Drosophila insulin-like peptide dilp8 and the neuropeptide-like precursor Nplp2 by the exoribonuclease Pacman/XRN1

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    Ribonucleases are critically important in many cellular and developmental processes and defects in their expression are associated with human disease. Pacman/XRN1 is a highly conserved cytoplasmic exoribonuclease which degrades RNAs in a 5' - 3' direction. In Drosophila, null mutations in pacman result in small imaginal discs, a delay in onset of pupariation and lethality during the early pupal stage. In this paper, we have used RNA-seq in a genome-wide search for mRNAs misregulated in pacman null wing imaginal discs. Only 4.2% of genes are misregulated ±>2-fold in pacman null mutants compared to controls, in line with previous work showing that Pacman has specificity for particular mRNAs. Further analysis of the most upregulated mRNAs showed that Pacman post-transcriptionally regulates the expression of the secreted insulin-like peptide Dilp8. Dilp8 is related to human IGF-1, and has been shown to co-ordinate tissue growth with developmental timing in Drosophila. The increased expression of Dilp8 is consistent with the developmental delay seen in pacman null mutants. Our analysis, together with our previous results, show that the normal role of this exoribonuclease in imaginal discs is to suppress the expression of transcripts that are crucial in apoptosis and growth control during normal development

    Management risk factors associated with foodborne disease outbreaks in the catering industry in England and Wales

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    Despite structured enforcement of food safety requirements known to prevent foodborne disease outbreaks, catering businesses continue to be the most common setting for outbreaks in England and Wales. Limited published evidence suggests that the way catering businesses are managed and operated may contribute to food safety control failures which in turn can result in an outbreak. The purpose of this study, funded by the Food Standards Agency1,2 was to identify the underlying management factors that may contribute to or prevent outbreaks in the catering industry. A matched case control study compared the management and operational practices of 148 catering businesses associated with foodborne outbreaks with 148 control catering businesses. High response rates were achieved: case businesses 90%, and control businesses 93%. To minimise false inferences from chance associations analysis followed a predefined hypothesised causal pathway. Hazard analysis critical control point systems and formal food hygiene training were found not to be protective and food hygiene inspection scores were not useful in predicting which businesses were likely to be associated with outbreaks. Larger small medium sized (SME) businesses were more likely to be associated with outbreaks compared to micro SME businesses. Operational and management practices did not differ significantly between case and control businesses when adjusted for SME size. SME size was not explained by other staff employment and management variables. However, businesses associated with Salmonella outbreaks were significantly more likely to use regional egg suppliers, the only significantly independent operational practice associated with Salmonella outbreaks. Regional egg suppliers were also more likely to supply businesses associated with outbreaks that were attributed to food vehicles containing eggs. Businesses associated with egg outbreaks were less likely to use eggs produced under an approved quality assurance scheme suggesting that the underlying risk associated with using regional suppliers may relate to the use of contaminated eggs.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
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